Gas driven hydraulic pump



y 1961 J. D. MOELLER ETAL 2,986,094

GAS DRIVEN HYDRAULIC PUMP Filed Aug. 4, 1958 2 Shets-Sheet 1 INVENTORS JOHN a. mum:

"D R. SCARFF GERALD N. 5TURI1 '2 c ya? THHR ATTOR EY y 1961 J. D. MOELLER ETAL 2,986,094

GAS DRIVEN HYDRAULIC PUMP Filed Aug. 4, 1958 2 Sheets-Sheet 2 v Q a J THEIR ATTORNEY ED JOHN D. MOEUER r50 R. 3cm

:3 sumo r1. sru/m United States Patent F GAS DRIVEN HYDRAULIC PUMP John D. Moeller, Vandalia, Ted R. ScarlI, Troy, and Gerald M. Sturm, Sidney, Ohio, assignors to General Motors Corporation, Detroit, Mich., a corporation of Delaware Filed Aug. 4, 1958, Ser. No. 752,902

Claims. (Cl. 103-51) ,This invention pertains to pumps, and particularly to gas driven hydraulic pumps.

- In copending application Serial No. 734,185, filed May 9, 1958, now US. Patent No. 2,942,553, granted June 28, 1960, in the name of Moeller et al and assigned to the assignee of this invention, a gas driven hydraulic pump specifically designed for use in missiles is disclosed. The present invention relates to an improved gas driven hydraulic pump wherein the reversing valves for controlling the admission and exhaust of gaseous medium under pressure are mechanically actuated by the motor piston adjacent its stroke ends in one direction, and are hydraulically actuated by the hydraulic fluid being pumped in the other direction. In addition, the reversing valves are maintained in their adjusted positions by hydraulic fluid under pressure. Furthermore, in order to reduce friction between the pump pistons and their respective cylinder bores, the pumping pistons are supported by hydrostatic bearings utilizing the hydraulic fluid being pumped. Accordingly, among our objects are the provision of a reciprocating type gas driven hydraulic pump including means for mechanically actuating the reversing valves adjacent the stroke ends of the motor piston; the further provision of a pump of the aforesaid type including means utilizing the developed hydraulic pressure for maintaining the reversing valves in the open position and for moving the reversing valves to the closed position; and the still further provision of a gas driven hydraulic pump including hydrostatic bearing means for supporting the pumping pistons.

The aforementioned and other objects are accomplished in the present invention by utilizing an integral piston assembly having a pair of opposed pumping pistons and a single motor piston. Specifically, the gas driven hydraulic pump includes a housing having a cylinder therein with a pair of oppositely extending smaller diameter bores and an intermediate larger diameter bore connected therewith. The integral piston assembly includes a pair of oppositely extending pumping pistons which are disposed within the smaller diameter cylinder bores and an enlarged motor piston which is disposed within the larger diameter bore of the cylinder. The pumping piston divides the large cylinder bore into two expansible chambers which can be alternately subjected to gaseous fluid medium under pressure and exhaust so as to effect reciprocation of the piston assembly. Each pumping piston has a pair of axially spaced annular grooves formed therein. The outer groove in each pumping piston is connected by internal passage means to its respective pumping chamber, and the inner groove is connected by passage means to the opposite pumping cylinder. Accordingly, a small portion of the hydraulic fluid being pumped will flow into the outer hydraulic groove in one pumping piston and the inner groove of the other pumping piston, and thence flow to drain through the passage means connecting the inner groove of the one pumping piston and the outer groove 2,986,094 Patented May 30, 196 1 2 of the other pumping piston with the opposite pumping chamber so as to form a hydrostatic bearing for the pumping pistons.

The admission and exhaust of gaseous fluid medium to the opposed expansible chambers formed by the motor piston is controlled by a pair of reversing valves; Each reversing valve includes a plunger portion which extends into one of the motor chambers when the re versing valve is exhausting its respective motor chamber. In addition, each reversing valve includes a piston portion disposed within a servo chamber of the housing that presents opposed surfaces of equal area which can be subject respectively, to hydraulic pressure for either maintaining the reversing valve in adjusted position, or moving the reversing valve to the exhausting posi: tion. Each servo chamber is connected by a passage with the high pressure hydraulic fluid outlet passage, and with the pumping chamber through a restricted orifice. In addition, the servo chambers are interconnected by four passages, two adjacent the ends of each servo chamber and two intermediate the ends of each servo chamber. The interconnecting passages are arranged so that upon movement of the motor piston to one of its stroke end positions, one of the reversing valves is mechanically moved to the admitting position, this movement of the reversing valve porting hydraulic fluid under pressure to the servo chamber of the other reversing valve so as to move the other reversing valve to the exhausting position. Thereafter, the other reversing valve is maintained in the exhausting position by hydraulic fluid under pressure, and

. the first mentioned reversing valve is maintained in the admitting position by hydraulic fluid under pressure. Accordingly, as long as gaseous fluid medium under pressure is supplied to the inlet ports of the reversing valves, and there is a demand for hydraulic pressure in the hydraulic system to which the pump is connected, the unitary piston assembly will be maintained in a state of continuous reciprocation.

Further objects and advantages of the present invention will be apparent from the following description, reference being had to the accompanying drawings, wherein a preferred embodiment of the present invention is clearly shown.

In the drawings:

Figure 1 is a schematic view of a gas actuated hydraulic pump constructed according to this invention.

Figure 2 is a view in elevation of a structural embodiment of the pump.

Figure 3 is a view, partly in section and partly in elevation, with certain parts broken away, taken generally along line 3-3 of Figure 2.

With particular reference to Figure 1, a gas driven hydraulic pump is shown schematically embodied in a housing 10 having an inlet 12 through which gaseous medium under pressure is admitted and an outlet 14 through which gaseous medium is exhausted. In addition, the housing 10 includes an inlet 16 for hydraulic fluid and an outlet 18 for hydraulic fluid. A cylinder is formed within the housing having a pair of oppositely extending smaller diameter bores 20 and 22 constituting pumping chambers and an intermediate larger diameter bore 24 constituting a motor chamber. An integral piston assem bly 26 is disposed within the cylinder comprising a motor piston 28 which divides the cylinder bore 24 into a pair of expansib le chambers 30 and 32. The motor piston 28 carries a pair of suitable sealing rings 34 which engage the bore of the cylinder. In addition, the piston assembly 26 includes pumping pistons 36 and 38 which are disposed within the pumping chambers 20 and 22, respec tively.

The pumping piston 36 is formed with a pair of spaced annular grooves 40 and 42, and the pumping piston 38 3 likewise includes a pair of spaced annular grooves 44 and 46. The annular groove 40 in the pumping piston 36 and the annular groove 46 in the pumping piston 38 are connected with an axial passage 48 that communicates with the pumping chamber 20. The annular groove 42 in the pumping piston 36 and the annular groove 44 in the pumping piston 38 are connected with a passage 50 that communicates with the pumping chamber 22. The function of the passages and annular grooves in the pumping pistons will be described more particularly hereinafter.

The inlet 16 for hydraulic fluid connects with passages 52 and 54, the passage 52 communicating with a one-way inlet check valve 56 through which hydraulic fluid is admitted to the pumping chamber 20. The passage 54 communicates with inlet check valve 58 through which fluid is admitted to pumping chamber 22. The outlet 18 connects with passages 60 and 62, passage 60 connecting with a one-way outlet check valve 64 which communicates with the pumping chamber 20, and the passage 62 connecting with a one-way check valve 66 which communicates with the pumping chamber 22. Accordingly, upon movement of the integral piston assembly 26 to the left, as viewed in Figure 1, the hydraulic fluid in the pumping chamber 20 will be delivered through check valve 64 and the passage 60 to the outlet 18 while pumping chamber 22 will be supplied with hydraulic fluid from the inlet 16 through passage 54 and check valve 58. Conversely, upon movement of the piston assembly 26 to the right, as viewed in Figure l, fluid will be delivered from pumping chamber 22 while fluid is admitted to the pumping chamber 20. Moreover, the area of the motor piston 28 is appreciably greater than the area of the pumping pistons 36 and 38, so that the pressure potential of the hydraulic fluid being pumped will be greater than the pressure of the gaseous medium admitted to the motor chambers. For example, if the area of the motor piston 28 is four times the area of the pumping piston 36, the pressure potential of fluid delivered to the outlet 18 will be approximately four times the potential of the gaseous pressure admitted to the motor chambers. Moreover, hydraulic fluid under pressure is continously delivered by the pump, since when one pumping piston is effecting its intake stroke, the other pumping piston is effecting its delivery stroke The unitary piston assembly 26 is maintained in a state of continuous reciprocation, when there is a demand for flow of hydraulic fluid under pressure in the system to which the outlet 18 is connected, by a pair of reversing valves generally indicated by numerals 68 and 70. The reversing valve 68 includes a piston portion 72, an inlet valve 74, an exhaust valve 76 and a plunger portion 78. The reversing valve 70 likewise includes a piston portion 80, an inlet valve 82, an exhaust valve 84 and a plunger portion 86. The plunger portions 78 and 86 of the reversing valves 68 and 70 extend into the expansible motor chambers 30 and 32, respectively, when the inlet valves 74 and 82, respectively, are closed. The inlet valve 74 is engageable with a valve seat 88 and exhaust valve 76 is engageable with a valve seat 90. The inlet and exhaust valves 74 and 76 control the connection of motor chamber 30 with either a pressure passage 92 or an exhaust passage 94, the pressure passage 92 being connected to the pressure inlet 12 and exhaust passage 94 being connected to the exhaust outlet 14. Similarly, the inlet valve 82 is engageable with a valve seat 96 and exhaust valve 84 is engageable with valve seat 98, the valves 82 and 84 controlling the connection of motor chamber 32 with the pressure passage 92 and the exhaust passage 94.

The piston 72 of the reversing valve 68 has end surfaces 100 and 102 of equal area exposed to servo chambers 104 and 106, respectively. In addition, the piston 72 has a pair of annular grooves 108 and 110. The annular groove 108 connects with a passage 112 in the housing by means of a radial piston passage 114 and an axial passage 116 formed in the valve rod 118. The passage 112 connects with passage 52 and hence the inlet 16 for hydraulic fluid. The inlet 16 is connected to a sump, or reservoir, not shown, containing a quantity of hydraulic fluid which may be maintained under a slight pressure. The annular groove in the piston 72 is utilized to interconnect passages 120 and 122, when the reversing valve 68 is actuated so that the inlet valve 74 is open and the exhaust valve 76 is closed. Passage 122 connects with the passage 60, and hence this passage is subjected to the delivery pressure of the pump. Chamber 104 is connected to a restricted orifice 124 to the inlet side of the outlet check valve 64. In addition, servo chamber 104 is connected to a passage 126. Servo chamber 104 is also connected to a passage 128, and servo chamber 106 is connected to passage 130.

The piston 80 likewise includes opposed end surfaces 132 and 134 of equal area which are exposed to servo chambers 136 and 138, respectively. In addition, the piston 80 is formed with a pair of annular grooves 140 and 142, and the annular groove 140 communicating at all times with passage 144 through radial piston passage 146 and axial passage 148 in the valve rod 150. The passage 144 connects with the passage 54 and the inlet 16 for hydraulic fluid. The annular groove 142 interconnects passages 126 and 152, as depicted in Figure 1, when the exhaust valve 84 is closed the inlet valve 82 is open. The passage 152 connects with the passage 62 and the outlet 18 for hydraulic fluid under pressure, while the passage 126 is connected with the servo chamber 104 for the reversing valve 68. The servo chamber 138 is connected to passage 128 which also connects with the servo chamber 104 of the reversing valve 68. The servo chamber 136 is connected through a restricted orifice 154 to the inlet side of the outlet check valve 66.

Operation of the gas driven hydraulic pump is as follows. The gaseous fluid medium admitted to the inlet 12 flows through passage 92 to the inlets of the reversing valves 68 and 70. In the position shown in Figure 1, the inlet valve 82 of the reversing valve 72 is open and the exhaust valve 76 of the reversing valve 68 is open. Accordingly, gaseous fluid medium under pressure will be admitted to the motor chamber 32 while the motor chamber 30 is connected to exhaust. Therefore, the integral piston assembly 26 will move to the left as viewed in Figure 1 whereupon the pumping piston 36 will deliver fluid under pressure while the pumping piston 38 is effecting its intake stroke. The reversing valve 70 is maintained in the gas admitting position by hydraulic fluid under pressure from passage 62, passage 152, the annular groove 142, the passage 126, servo chamber 104, passage 128 and the servo chamber 138. The pressure in the servo chamber 138 maintains the reversing valve 70 in the position shown in Figure l, and the pressure in servo chamber 104 maintains the reversing valve 68 in the exhaust position as shown in Figure 1. At this time, the servo chamber 136 of the reversing valve 70 is connected to drain through restricted orifice 154, and the servo chamber 106 of the reversing valve 68 is connected to drain through passage 130, the annular groove 140 of the piston 80, radial passage 146, axial passage 148 in the valve rod and passage 144.

As the motor piston 28 approaches the end of its stroke to the left, as viewed in Figure 1, the left-hand side of the piston 28 will engage the plunger 78 so that continued movement of the piston assembly 26 to the left will effect movement of the reversing valve 68 to the left so as to move the inlet valve 74 out of engagement with its valve seat 88 and move the exhaust valve 76 into engagement with its valve seat 90. During this movement, the hydraulic fluid in servo chamber 104 is forced through restricted orifice 124. When the exhaust valve 76 engages its seat 90 and the inlet valve 74 is open, the reversing valve 68 is in the admitting position whereupon gaseous fluid medium under pressure will be admitted to the motor chamber 30 from passage 92. Moreover, when the exhaust valve 76 engages its valve seat 90, the passages 120 and 122 will be interconnected by the annular groove 110 in the piston'72, whereupon high pressure fluid from the passage 60 will flow through passages 120 and 122 to the servo chamber 136 associated with the piston 80 of the reversing valve 70. Simultaneously, the servo chamber 138 will be connected to drain through passage 128, annular groove 108, radial passage '114, axial passage 116 in the valve rod 118 and passage 112 to the passage 52. Accordingly, the pressure fluid in the servo chamber 136 will move the piston 80 and the reversing valve 70 to the left so that the inlet valve 82 will engage its seat 96 and the exhaust valve 84 will be open. Therefore, the motor chamber 32 will be connected to exhaust while the motor chamber 30 is connected to pressure and the integral piston assembly 26 will move to the right. During movement of the piston assembly 26 to the right, the reversing valve 68 is maintained in its admitting position by hydraulic pressure in servo chamber 106 which is connected by passage 130 to the servo chamber 136 of the reversing valve 70. Accordingly, the pumping piston 38 will deliver hydraulic fluid under pressure through check valve 66 to the passage 62 in outlet 18, While the pumping piston 36 eifects its intake stroke by drawing fluid from the inlet 16 through passage 52 and inlet check valve 56.

4 As the piston assembly approaches its right-hand stroke end position, the motor piston 28 will engage the plunger 86 of the reversing valve 70, so as to mechanically move the reversing valve 70 to the admitting position, thereby enabling the piston portion 80 of the reversing valve 70 to complete the hydraulic connections to the reversing valve 68 so as to move the reversing valve 68 to the exhausting position. Thus, the unitary piston assembly 26 will be maintained in a state of continuous reciprocation and fluid under pressure will be continuously supplied to the outlet 18.

During reciprocation of the unitary piston assembly 26, the pumping pistons 36 and 38 are supported by a hydrostatic bearing for reducing friction to a minimum. The pumping pistons 36 and 38 are snugly received within their respective bores 20 and 22, and the hydrostatic bearing means are supplied with fluid from the pumping chamber in which the piston is effecting the delivery stroke. Thus, when the unitary piston assembly 26 is moved to the left, as viewed in Figure 1, a portion of the hydraulic fluid under pressure in the pumping chamber 20 flows through passage 48 to the annular groove 40 in the pumping piston 36 and 46 in the pumping piston 38. Since the pumping chamber 22 is being expanded, the high pressure fluid admitted to grooves 40 and 46 will flow around the periphery of the piston towards annular grooves 42 and 44 which are connected to the pumping chamber 22 through passage 50. This film of hydraulic fluid constitutes a hydrostatic bearing for supporting the pumping pistons 36 and 38. Conversely, when the pumping chamber 22 is pressurized due to movement of the unitary piston assembly to the right, the pumping chamber 20 is being expanded so that high pressure fluid admitted to grooves 44 and 42 through passage 50 will flow to the pumping chamber 20 through grooves 46 and 40 and passage 48.

With particular reference to Figures 2 and 3, the structural embodiment of the gas driven hydraulic pump will be described. The pumping housing comprises end caps 160 and 162 and four intermediate cylindrical blocks 164, 166, 168 and 170. The end caps and cylindrical blocks are held in assembled relation by a plurality of through bolts indicated by numeral 172. The cylindrical block 164 contains the outlet check valve 64 and supports the piston 72 of the reversing valve 68. The piston 72 is supported for reciprocable movement in a guide 174 and the exhaust inlet valve seat 88 and the exhaust valve seat 90 for the valve 74 and 76, respectively, are formed in a guide 176 carried by the cylindrical block 166. The high pressure outlet 18 is formed in the block 166 as is the pumping chamber 20. The motor chamber 24 is formed in cylindrical block 168, the block 168 also including the low pressure hydraulic inlet 16. The inlet 12 for gaseous medium'under pressure and the exhaust on the outlet '14 for gaseous medium are also formed as a part of the cylin-' drical block 168, these portions being cut away in Figure 3. A valve guide 178 is formed with an exhaust valve seat 98 and the inlet valve seat 96 of the reversing valve 70, While the piston of the reversing valve 70 is supported in a guide 180 carried by the cylindrical block 17 0. The cylindrical block also supports the outlet check valve 66 and the inlet check valve 58. The inlet check valve 56 is supported within a cylindrical bore of the cylindrical block 164, in a manner similar to that of inlet valve 58. The hydraulic connections of the several valves are shown schematically in Figure l, and hence are not described in connection with the structural embodiment shown in Figure 3.

While the embodiments of the invention as herein disclosed constitute preferred forms, it is to be understood that other forms might be adopted.

What is claimed is as follows:

1. A gas driven hydraulic pump including, a cylinder having oppositely extending end bores of the same diameter and an intermediate bore of different diameter, an integral piston assembly disposed within said cylinder having a pair of pumping pistons disposed within said end bores whereby said end bores constitute pumping chambers and a motor piston disposed within said intermediate bore, said motor piston dividing said intermediate bore into a pair of opposed chambers, inlet and outlet check valves communicating with said pumping chambers, hydrostatic bearing means supporting each pumping piston and having hydraulic communication with both of said pumping chambers to circulate a portion of the fluid being pumped around the periphery of said pumping pistons due to the pressure differential between said pumping chambers, reversing valve means for controlling the alternate admission and exhaust of fluid under pressure to the exposed motor chambers, and means for actuating said reversing valve means adjacent the stroke ends of said motor piston.

2. A gas driven hydraulic pump including, a cylinder having oppositely extending end bores of the same diam eter and an intermediate bore of dilferent diameter, an integral piston assembly disposed within said cylinder having a pair of pumping pistons disposed within said end bores whereby said end bores constitute pumping chambers and a motor piston disposed within said intermediate bore, said motor piston dividing said intermediate bore into a pair of opposed chambers, inlet and outlet check valves communicating with said pumping chambers, a pair of reciprocable reversing valves communicating with said motor chambers for controlling the alternate admission and exhaust of fluid under pressure to the opposed motor chambers, each reversing valve being mechanically actuated by said integral piston assembly adjacent the stroke ends of said motor piston for alternately admitting fluid under pressure to said motor chambers, and servo means connecting said reversing valves with said pumping chambers for alternately moving each reversing valve to an exhausting position and maintaining the other reversing valve in the admitting position.

3. The gas driven hydraulic pump set forth in claim 2 wherein each reversing valve includes an inlet valve and an exhaust valve.

4. The gas driven hydraulic pump set forth in claim 2 wherein each reversing valve includes a piston disposed within a servo chamber, each piston presenting opposed surfaces of equal area to said servo chamber.

5. The gas driven hydraulic pump set forth in claim 4 wherein each reversing valve piston includes a pair of spaced annular grooves, passage means connecting an intermediate portion of each servo chamber with the outlet side of one of said outlet check valves, restricted orifice means connecting one end of each servo chamber with the inlet side of each outlet check valve, a plurality of passages interconnecting said servo chambers, and means cementing one of the annular grooves in each piston with the inlet side of one of said inlet check valves whereby mechanical actuation of said reversing valves by said integral piston assembly will complete a flow path to effect servo actuation of the other reversing valve.

6. A gas driven hydraulic pump including, a cylinder having oppositely extending end bores of the same diameter and an intermediate bore of larger diameter, an integral piston assembly disposed within said cylinder having a pair of pumping pistons disposed within said end bores whereby said end bores constitute pumping chambers and a motor piston disposed within said intermediate bore, said motor piston dividing said intermediate bore into a pair of opposed chambers, inlet and outlet check valves communicating with said pumping chambers, 21 pair of reciprocable reversing valves communicating with said motor chambers for controlling the alternate admission and'exhaust of gas under pressure to the opposed motor chambers, each reversing valve including a plunger portion which extends into its respective chamber when the respective reversing valve is in an exhausting position whereby one reversing valve will be mechanically actuated by said motor piston adjacent each stroke end thereof to an. admitting position, and a servo actuated means operatively connected to each reversing valve for moving the other reversing valve to an exhausting position, said servo actuated means being controlled by mechanical actuation of the reversing valves adjacent the stroke ends of said motor piston.

7. The gas driven hydraulic pump set forth in claim 6 wherein each reversing valve includes a piston disposed within a servo chamber, and wherein said servo chambers are connected by passage means with the outlet side of said outlet check valves.

' 8. A gas driven hydraulic pump including, a cylinder having oppositely extending end bores of the same diameter constituting pumping chambers, and an intermediate bore of difierent diameter, an integral piston disposed within said cylinder having a pair of pumping pistons disposed within said pumping chambers and a motor piston disposed Within said intermediate bore, said motor piston dividing said intermediate bore into a pair of opposed chambers, inlet and outlet check valves communicating with said pumping chambers, reversing valve means for controlling the alternate admission and exhaust of gas under pressure to the opposed motor chambers, means for actuating said reversing valve means adjacent the stroke ends of said motor piston, hydrostatic bearing means supporting said integral piston assembly comprising a pair of spaced annular grooves in each pumping piston, and passage means in said pumping pistons connecting one groove of each pumping piston with each pumping chamber to circulate a portion of the fluid being pumped around the periphery of said pumping pistons due to the pressure differential between said pumping chambers.

9. The gas driven hydraulic pump set forth in claim 8 wherein said passage means comprise a first passage connecting one of said pumping chambers with the outer annular groove of the pumping piston disposed within said one pumping chamber and the inner annular groove of the pumping piston disposed within the other pumping chamber, and a second passage connecting said other pumping chamber with the outer annular groove of the other pumping piston and the inner annular groove in said one pumping piston whereby said pumping pistons are supported by a film of hydraulic fluid being pumped during movement of said integral piston assembly in both directions.

10. A gas driven hydraulic pump including, a cylinder having oppositely extending end bores of the same diameter and an intermediate bore of different diameter, an integral piston assembly disposed within said cylinder having a pair of pumping pistons disposed within said end bores whereby said end bores constitute pumping chambers and a motor piston disposed within said intermediate bore, said motor piston dividing said intermediate bore into a pair of opposed chambers, inlet and outlet check valves communicating with said pumping chambers, a pair of reciprocable reversing valves for controlling the alternate admission and exhaust of fluid under pressure to the opposed motor chambers, passage means connecting each reversing valve with one of said motor chambers, said reversing valve being mechanically actuated by said integral piston assembly adjacent the stroke ends of the motor piston for alternately admitting fluid under pressure to said motor chambers, and servo actuated means for alternately moving each reversing valve to an exhausting position and maintaining the other reversing valve in the admitting position, said servo actuated means being controlled by mechanical actuation of the reversing valves adjacent the stroke ends of said motor piston.

References Cited in the file of this patent UNITED STATES PATENTS 495,334 Hillenbrand Apr. 11, 1893 1,025,163 Schreidt May 7, 1912 1,714,425 Knab May 21, 1929 2,296,647 McCormick Sept. 22, 1942 2,337,821 Huber Dec. 28, 1943 2,445,985 Werner July 27, 1948 

